Final answer:
The ingredient that is both calming and an antiseptic is 4-hexylresorcinol, known for its effective germicidal properties and minimal side effects, widely used in mouthwashes and antiseptic preparations for the skin.
Step-by-step explanation:
The ingredient that is known for being both calming and an antiseptic is 4-hexylresorcinol. This compound is powerful enough to serve as a germicide, yet it is gentle enough to be used in mouthwashes and throat lozenges due to its soothing properties. 4-hexylresorcinol stands out because it provides effective antiseptic action with fewer undesirable side effects, making it a safer phenolic antiseptic compared to others. Furthermore, it is utilized in antiseptic preparations for skin application.
Additional calming and antiseptic ingredients include substances such as witch hazel, which is often used in skin care products due to its astringent properties, as well as silver, which has long-standing uses in preventing infection and aiding antibiotic effectiveness. However, ingredients such as triclosan, which were once widespread in antibacterial products, have seen regulatory changes due to safety and efficacy concerns.